Editors' Disclosures: Christine Laine, MD, MPH, Editor in Chief, reports that she has no financial relationships or interests to disclose. Darren B. Taichman, MD, PhD, Executive Deputy Editor, reports that he has no financial relationships or interests to disclose. Cynthia D. Mulrow, MD, MSc, Senior Deputy Editor, reports that she has no relationships or interests to disclose. Deborah Cotton, MD, MPH, Deputy Editor, reports that she has no financial relationships or interest to disclose. Jaya K. Rao, MD, MHS, Deputy Editor, reports that she has stock holdings/options in Eli Lilly and Pfizer. Sankey V. Williams, MD, Deputy Editor, reports that he has no financial relationships or interests to disclose. Catharine B. Stack, PhD, MS, Deputy Editor for Statistics, reports that she has stock holdings in Pfizer and Johnson & Johnson.

Abstract

Background:

Suicide prevention programs have become ubiquitous among military units; identifying temporal trends and nonclinical factors associated with the chosen suicide methods may help improve suicide prevention strategies.

Objective:

To calculate suicide rates of active duty military personnel and identify those who are at risk for firearm-specific suicide.

Design:

Retrospective cohort study.

Setting:

Military units in the United States.

Patients:

All active duty enlisted U.S. military personnel from 2005 to 2011.

Measurements:

Suicide rates per 100 000 were calculated for each branch. Adjusted odds ratios for firearm-specific suicide were calculated with 95% CIs.

Results:

1455 military personnel committed suicide from 2005 to 2011. From 2006 to 2011, the rates were highest among army personnel (19.13 to 29.44 cases per 100 000). Among suicides with a known cause of death, 62% were attributed to firearms. The results of this study also suggest that among army personnel or marines who committed suicide, those with infantry or special operations job classifications were more likely than those in noninfantry positions to use a firearm.

These results may help inform policymakers and advisors about differences in risks of suicide and violent suicide among the armed services and may help guide efforts to prevent self-harm within the military.

Primary Funding Source:

None.

Suicide rates have increased by 60% worldwide during the past 47 years and is a leading cause of death among 15- to 44-year-olds (1). In 2010, suicide was the 10th leading cause of death in the United States (2). The overall suicide rate in the U.S. military has also increased, almost doubling from 2001 to 2011 (3).

Potential factors that have changed over time, such as deployments and mental health conditions, have helped clarify the reasons for the increased suicide rate in the U.S. military. A recent study of suicide risk among veterans found that deployment did not increase the risk for suicide (4), whereas other studies explored risk for suicide after psychiatric hospitalization (5) as well as psychosocial risk (6).

Research and debate are ongoing regarding the various motivations for choosing a particular method of suicide (7, 8). Previous studies showed that men are more likely to use violent methods of suicide (for example, firearm related), whereas women are more likely to use nonviolent means (for example, poisoning) (8). Within the military, research suggests that the suicide risk is significantly greater among personnel whose occupations provide easy access to firearms than among those in other occupations (9). Some researchers have suggested that both psychological and biological differences exist between people who choose violent methods and those who use nonviolent ones (10, 11). Empirical evidence suggests that among military conscripts, previous problems in school may predict violent suicide attempts, which also may be a strong indicator of subsequent suicide (12). Indeed, violent suicide attempts have been linked very strongly to subsequent suicide completion (12). In fact, a person who attempts suicide by firearm has a risk for subsequent completed suicide about 5 times higher than that of people who attempt suicide by nonviolent means (hazard ratio [HR], 5.18 [95% CI, 1.27 to 21.24]) (12).

A common limitation in previous analyses evaluating suicide trends in the U.S. military was a lack of consolidated service data. Before 2008, risk factor analyses for U.S. Department of Defense (DOD) suicides were performed in relatively small populations, primarily at the military service level, by using service-unique databases (6). Moreover, the bulk of research has focused on the army (4, 5, 13–18), whereas studies including all services have been limited to survey-type data or have had limited follow-up (16–18).

The objective of the present study is to evaluate suicide rates among active duty military personnel across years and to identify differences among branches. Further, with regard to completed suicides, we aim to identify the groups of active duty military personnel who are at greatest risk for firearm-specific suicide.

Methods

A joint endeavor by the Defense Suicide Prevention Office and the U.S. Department of Veterans Affairs resulted in development of the Suicide Data Repository (SDR), which has mitigated the problem of insufficient consolidated data. The SDR combines data from the Centers for Disease Control and Prevention (CDC) via the National Death Index (NDI), as well as the Military Mortality Database, to provide a collection of demographic and military-specific information on all service members and veterans who committed suicide and had served in the armed forces since 1974. The SDR was fully established in 2013 and to our knowledge is the most comprehensive source of demographic and military-specific data on suicides in the U.S. military. The data for this study were provided by the Defense Manpower Data Center (DMDC).

Study Population

We used 2 data sets: The first, extracted from the SDR, contains demographic and military-specific data for each suicide; the second contains the monthly end strength, or personnel count on the last day of the month, for each demographic subpopulation. All subpopulation strata were combinations of the following: year, sex, age, race, marital status, education, age at enlistment, rank, and Armed Forces Qualification Test (AFQT) category (higher AFQT categories represent lower cognitive ability; for example, category IIIB or higher is equal to a percentile score <50). Data on active duty personnel were not fully available for suicides occurring before 2005 or for those occurring outside the United States. Therefore, our study population comprises all enlisted personnel (that is, nonofficers) of the U.S. military regular component (including the army, air force, navy, and marines) who committed suicide while on active duty stateside between 2005 and 2011. For the analysis of firearm-specific suicides, we attempted to exclude suicides among enlistees who did not have military service exposure and perhaps had an unrecognized predisposition to suicidality before entering the military; therefore, we included only those who had already completed training. The DOD Human Research Protection Program and Naval Postgraduate School's Institutional Review Board approved the collection of the data for this study (NPS.2014.0073).

Statistical Analysis

Temporal Trends of Active Duty Military Suicide

Using the combined data set containing both suicides and personnel counts, we determined the branch-specific suicide rates. Service branches have different missions and recruit and attract different types of personnel; because we could not control for these differences with our available data, we analyzed data for each branch separately.

Predictors of Violent Methods Among Active Duty Military Suicides

Using the cohort of completed suicides in the SDR data set, we identified predictors of firearm-specific suicide. Predictor variables included factors previously identified in the literature and a priori hypothesized to affect both the service and the outcome. To evaluate the total effect of each military branch on firearm-specific suicide, we considered several covariates, including age at death, rank, sex, education, race, marital status, religion, length of service at the time of death, AFQT score category, and primary military occupation (that is, infantry/special operations). We identified covariates to adjust for in multivariable models using a directed acyclic graph approach (representing the relationships among service, suicide, and other variables) to determine minimally sufficient adjustment sets (19) (Appendix Figure). The minimally sufficient adjustment set identified included infantry/special operations job classification, age, sex, AFQT score category, and education. We restricted the multivariable models identifying predictors of firearm-specific suicide to men, because more than 95% of all suicides were committed by men (only 1 female marine and 9 female navy personnel committed suicide). Among the navy and air force suicides, we did not consider infantry/special operations job classification in multivariable models because only 2 suicides were identified and this job classification is found more commonly in the army and marines.

Appendix Figure.

Directed acyclic graph evaluating the relationship between branch of service and firearm-specific suicide and potential confounders.

AFQT = Armed Forces Qualification Test; ops = operations.

Of 1416 suicides, 366 (25.8%) had missing data for firearm-specific suicide or covariates (Appendix Table 1). We used multiple imputation to address missing data, and we assumed data were missing at random. The variables included in the imputation models included method of suicide, AFQT score category, education, infantry/special operations job classification, sex, and age; imputations were run separately by branch. We specified conditional models and performed the imputations based on these conditional models. We generated multiple sets (m = 10) of imputed values, allowing us to account for the uncertainty inherent in using the imputed values in our models (20, 21). The imputed data sets were combined by applying Rubin rules (22, 23), which are used to appropriately adjust estimated SEs, and thus CIs and P values, to account for the additional uncertainty associated with data missingness. Because the mechanism of these missing data is unknown and may not be consistent with the missing-at-random assumption, these results should be interpreted cautiously. In a secondary analysis, we compared multiple imputation results with a complete case analysis approach, excluding observations with missing data. Adjusted odds ratios (aORs) are reported with 95% CI. Data were analyzed using R version 3.1.2 (R Foundation for Statistical Computing) (24). The base package was used for the logistic models, and the mice (Multiple Imputation by Chained Equations) package (25) was used for the multiple imputation analyses.

Appendix Table 1. Selected Variables and Percentage With a Missing Cause of Suicide

Appendix Table 1. Selected Variables and Percentage With a Missing Cause of Suicide

Role of the Funding Source

This study was unfunded.

Results

A total of 1455 suicides occurred during 125 million person-months among the active duty, regular component enlisted personnel in the U.S. Army, Air Force, Marine Corps, and Navy from 2005 to 2011, with an average end strength for that period of 451 000, 268 000, 173 000, and 283 000, respectively. The highest suicide rates (per 100 000) from 2005 to 2011 were in the army in 2009 and 2010 (29.44 and 29.15 suicides, respectively) (Figure and Table 1), whereas the lowest suicide rates were in the air force and navy in 2005 (9.95 and 9.79 suicides, respectively). From 2006 to 2011, the rates were higher among army personnel (19.13 to 29.44 cases per 100 000) than among members of any other branch.

Figure.

Suicide rates per 100 000 persons (2005 to 2011), by branch of service.

Characteristics

Of these suicides, 1416 occurred among nontrainees, comprising our suicide cohort (Table 2). Most (52.5%) were among army personnel, and approximately 95% occurred in men. The median age was 25 years (interquartile range [IQR], 22 to 30 years) across all branches; however, suicides among marines seem to have occurred in younger personnel than those among members of the other services (22 years [IQR, 20 to 25]). Approximately 60% of suicides occurred in the lower enlisted ranks (E1 to E4). In the navy and air force, fewer than 50% of suicides were in lower enlisted ranks, whereas in the army, 66.9% of suicides occurred in lower enlisted ranks. The lower ranks in the marines accounted for more than 70% of suicides in that branch. More than 75% of suicides were carried out by white service members across all branches, with little difference among branches, although a higher percentage (85.2%) of suicides occurred in marines who were white. Among service members who committed suicide, little difference in marital status was observed among the branches, although the air force had the lowest proportion of suicides (34.7%) in those who were never married. More than 87% of suicides occurred in service members with only a high school diploma; more than 95% occurred in marines with only a high school diploma. Nearly half the suicides (45.6%) in the navy were carried out by members who claimed no religious preference. In contrast, one quarter (26.3%) of the suicides in the army and less than one quarter (22.9%) in the marines and air force occurred in those who claimed no religious preference. Among service members who committed suicide, the median length of service was 4 years (IQR, 2 to 8 years), with army personnel and marines having the 2 shortest median lengths of service (3 and 2 years, respectively). Across all branches, the largest proportion of suicides (38.8%) occurred among those in AFQT category II. More than half of all suicides in the air force and navy were carried out by members in category I or II (50.8% and 51.8%, respectively).

Firearms were the primary cause of death (47.9%) across all branches as well as for each branch. Among suicides with a known cause, firearms accounted for 62.3%. Within the navy, personnel with an aircraft-related primary occupation made up the second largest proportion of suicides (19.0%); however, the largest proportion of suicides (32.3%) in the navy occurred among personnel in positions outside the common job classifiers. Among army personnel who died by suicide, the most common job classifier was infantry or special operations (24.2%); one quarter (25.0%) of air force suicides occurred among personnel with aircraft-related primary occupations, and nearly one third (32.4%) of marine suicides were carried out by those in the infantry or special operations.

Odds of Firearm-Specific Suicide

In both the army and marines, the odds of a service member committing suicide with a firearm were twice as great if he or she had an infantry or special operations job classification than if he or she had any other job classification (aOR, 2.09 [CI, 1.32 to 3.32] for the army; aOR, 2.70 [CI, 1.17 to 6.23] for the marines), after adjustment for known confounders (Table 3). The odds of a service member in the army committing suicide with a firearm were 1.47 times higher if he or she was in AFQT category IIIB or higher than if he or she was in AFQT category I (that is, had greater cognitive ability) (aOR, 1.47 [CI, 1.02 to 2.12]), after adjustment for known confounders. Lastly, among air force personnel, those who had completed some college courses had 0.36 times the odds of committing suicide with a firearm than those with no college education (aOR, 0.36 [CI, 0.15 to 0.91]), after adjustment for known confounders. The complete case analyses provide similar estimates (Appendix Table 2).

Table 3. Adjusted Odds Ratios of Firearm-Specific Suicide Among Men*

Table 3. Adjusted Odds Ratios of Firearm-Specific Suicide Among Men*

Discussion

In this study, we found that from 2005 to 2011, the active duty, regular component enlisted service members most at risk for suicide were in the army. In addition, the navy, air force, and army all had increasing rates of suicide over time, with the greatest increase in the army. Our results also suggest that among the army and marine personnel who committed suicide, those with infantry or special operations job classifications were more likely than noninfantry personnel to use a firearm.

Clearly, a need exists to identify military personnel at risk for suicide and to provide them with necessary care. Identifying the service members most at risk is challenging for various reasons, including a resistance to seek care because of the fear of stigmatization or of jeopardizing one's career (26). The American Academy of Family Physicians has emphasized the need for clinicians first to identify at-risk service members by tailoring military-specific questions regarding their mental health (27). Although the risk dynamics of deployment history, job classification, and branch of service are not fully understood, assuming all military personnel are at risk and assessing them appropriately by using a validated screening tool may be an effective approach to reducing suicide attempts (28). Furthermore, clinicians should recognize the unique risks that firearms pose in this population: Not only do veterans have 4 times more firearms than nonveterans (29), they are more likely than nonveterans to use them to commit suicide (30).

Our results are particularly interesting in light of the recent mass shooting of military personnel in Chattanooga, Tennessee. As a result of this terrorist act, U.S. Secretary of Defense Ashton B. Carter, after a review of security policies at military facilities, authorized an increase in firearm presence among qualified DOD personnel at military installations (31). Concurrently, members of the U.S. House of Representatives proposed at least 3 bills aimed at repealing current restrictions on carrying firearms at military establishments (Enhancing Safety at Military Installations Act, H.R. 3115, 114th Cong. [2015 to 2016]) and at establishing the right to carry personally owned and government-issued firearms at recruitment offices (Military Recruiter Right to Carry Act of 2015, H.R. 3138, 114th Cong. [2015 to 2016]; Securing Military Personnel Response Firearm Initiative [SEMPER FI] Act, H.R. 3139, 114th Cong. [2015 to 2016]). However, this legislation may have unintended consequences, as increased access to firearms has been linked repeatedly to increased suicide and intimate partner violence (32).

The “healthy warrior effect” presumably would yield a lower suicide rate in the military than in the general population because of health screening on entry and periodic health assessments (33). However, there is little evidence that the current suicide rate among service members is lower than that of the general population; in fact, the rates in the present study are higher than those in the general population. For these reasons, any future research in the military population should at least consider mental health history, although its effect on suicide or choice of method remains unclear. As previously shown, access to firearms may increase a person's suicide risk (34), but this increased risk is not unique to individuals with a history of mental illness (35). Moreover, the risk for suicide as it pertains to firearm access may be an indicator more of impulsivity than of underlying mental illness. Previous research, if stratified by those with and those without a diagnosed mental illness, indicates there is no difference in firearm-specific suicide risk (35).

Our findings are similar to those of previous research evaluating firearm access and suicide risk among military service members in other countries. Among the Defence Forces of Ireland, 53% of suicides were the result of a firearm; however, nearly all suicides occurring during duty on a military base were caused by a firearm (36). Similarly, in the present study of U.S. active duty personnel, 48% of suicides were the result of a firearm; however, 62% of suicides with a known cause of death were attributed to firearms.

Two previous studies comparing suicide rates in the U.S. military with those in the civilian population found that the rate among civilians was approximately 2 times greater than the rate in military personnel (37, 38). These studies covered the period from 1980 to 1992, which includes a major war (that is, the Gulf War of 1990 to 1991); however, the long-term, indirect, and direct effects of combat operations could not have been seen. Moreover, although several previous studies of the armed forces of various countries found that the suicide rate among military personnel was consistently lower than that of the civilian comparison population (39–42), we found a higher suicide rate in the U.S. military than in the civilian population.

From 2006 to mid-2009, a period including the troop surge and subsequent drawdown in Iraq, the marines had the second highest suicide rates (Figure). The army's highest suicide rates occurred from 2009 to 2011, a period encompassing the drawdown in Iraq and a troop increase in Afghanistan. For these reasons, it is possible that several unique service-specific risk factors existed (that is, the surge in Iraq may have affected suicides among marines, whereas the change in mission emphasis affected suicides in the army). Although some recent research suggests that deployment may not be a risk factor for suicide (4), our research suggests that several factors may affect suicide risk, including combat operations in 2 separate theaters.

Alcohol and other factors may play important roles in suicide risk, perhaps even more than suicidal history. Stenbacka and Jokinen (12) recently found that among military conscripts with no history of attempted suicide, those who had a history of alcohol abuse or contact with police were at higher risk for completed suicide than those who did not have such a history. In addition, combat experiences previously were linked to alcohol misuse. In fact, the adjusted odds of alcohol misuse are greater for special operations personnel who engage in combat (aOR, 2.12 [CI, 1.51 to 2.98]) and for special operations personnel who are determined to be a threat to themselves (aOR, 1.60 [CI, 1.18 to 2.18]) than for special operations personnel without those specific characteristics (43). Similarly, Wilk and colleagues (44) estimated the odds of alcohol misuse among recently redeployed infantry personnel and found similar relationships between combat and alcohol misuse and threat to oneself and alcohol misuse.

Our findings are subject to various limitations. We included only active duty, regular component enlisted personnel. However, suicide rates in the U.S. military have been shown to be higher among enlistees and even higher for junior than senior enlistees (14, 18, 45). Suicide rates may vary among components and branches of service. Namely, a member may serve in the regular, National Guard, or reserve component, and each component differs in several ways (such as recruitment standards, operational objectives, and stressors). Although suicide is not unique to men, the generalizability of the analysis of predictors of firearm-specific suicide is limited to active duty enlisted men because of the scarcity of data on women who commit suicide. Our study considered only completed suicides and did not consider suicide ideation, plans, or attempts. It is possible that reduced access to firearms has resulted in a shift in preferred suicide methods in some services. Compared with other branches, among navy suicides with a known cause of death, the proportion attributed to firearms was the lowest (56%) and that attributed to pharmaceutical-related suicide was the highest (8%). In addition, in the analysis of predictors of firearm-specific suicide, the method was missing for 23% of the suicides, which may have biased our sample in an unknown direction. Without information about previous suicide attempts, we could capture only the completed suicides, biasing our sample toward methods with higher lethality. Although research suggests that a person who attempts suicide by violent means has a markedly high risk for subsequent completion (12), attempts with a firearm largely are successful. Therefore, when considering violent suicide methods, any examinations of subsequent completed suicide risk are somewhat limited by the method chosen.

Because of limitations within the source databases, our study includes only suicides occurring stateside. As such, we could not evaluate the suicide risk of service members on deployment. The DMDC, the DOD office that controls these data, does not yet have NDI data (CDC controlled) linked to the DOD records beyond 2011. Part of the DMDC's strategic data plan is to have updated NDI decedent data (through 2013 to 2014) matched with DOD personnel records by the end of 2016. For a more robust analysis, ideally a longitudinal data set matching records from the 2 data sets along with deployment, medical, and other histories would be constructed. To the extent that our classification of suicide methods was inaccurate, we acknowledge the possibility of bias in the firearm-specific suicide analysis, if there was differential misclassification of methods used among branches of the service. Lastly, because of a lack of information regarding ownership of the weapons used in these suicides, our results likely are not especially informative for policies regarding access to personally owned firearms on military installations.

Predictors of suicide and accident death in the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS): results from the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS).

Table 3. Adjusted Odds Ratios of Firearm-Specific Suicide Among Men*

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